Top set plug and method

ABSTRACT

A top set plug for sealing against a casing of a well. The plug includes a mandrel having a throughout bore that extends from a top end to a bottom end; a connecting mechanism located at the top end of the mandrel; a sealing element located around the mandrel and configured to be pushed toward an internal wall of the casing; an upper wedge configured to push the sealing element against the casing; and a slip ring configured to push the sealing element over the upper wedge and also to engage the inner wall of the casing with buttons for preventing the plug to slide along the casing.

BACKGROUND Technical Field

Embodiments of the subject matter disclosed herein generally relate todownhole tools used for perforating and/or fracturing operations, andmore specifically, to a downhole plug that is configured to be set fromits top.

Discussion of the Background

In the oil and gas field, once a well 100 is drilled to a desired depthH relative to the surface 110, as illustrated in FIG. 1, and the casing102 protecting the wellbore 104 has been installed and cemented inplace, it is time to connect the wellbore 104 to the subterraneanformation(s) 106 to extract the oil and/or gas. This process ofconnecting the wellbore to the subterranean formation may include a stepof isolating a stage of the casing 102 with a plug 112, a step ofperforating the casing 102 with a perforating gun assembly 114 such thatvarious channels 116 are formed to connect the subterranean formationsto the inside of the casing 102, a step of removing the perforating gunassembly, and a step of fracturing the various channels 116.

Some of these steps require to lower into the well 100 a wireline 118 orequivalent tool, which is electrically and mechanically connected to theperforating gun assembly 114, and to activate the gun assembly and/or asetting tool 120 attached to the perforating gun assembly. Setting tool120 is configured to hold the plug 112 prior to isolating a stage andalso to set the plug. FIG. 1 shows the setting tool 120 disconnectedfrom the plug 112, indicating that the plug has been set inside thecasing.

FIG. 1 shows the wireline 118, which includes at least one electricalconnector, being connected to a control interface 122, located on theground 110, above the well 100. An operator of the control interface maysend electrical signals to the perforating gun assembly and/or settingtool for (1) setting the plug 112 and (2) disconnecting the setting toolfrom the plug. A fluid 124, (e.g., water, water and sand, fracturingfluid, etc.) may be pumped by a pumping system 126, down the well, formoving the perforating gun assembly and the setting tool to a desiredlocation, e.g., where the plug 112 needs to be deployed, and also forfracturing purposes.

The above operations may be repeated multiple times for perforatingand/or fracturing the casing at multiple locations, corresponding todifferent stages of the well. Note that in this case, multiple plugs 112and 112′ may be used for isolating the respective stages from each otherduring the perforating phase and/or fracturing phase.

These completion operations may require several plugs run in series orseveral different plug types run in series. For example, within a givencompletion and/or production activity, the well may require severalhundred plugs depending on the productivity, depths, and geophysics ofeach well. Subsequently, production of hydrocarbons from these zonesrequires that the sequentially set plugs be removed from the well. Inorder to reestablish flow past the existing plugs, an operator mustremove and/or destroy the plugs by milling or drilling the plugs.

A typical frac plug for such operations is illustrated in FIG. 2 andincludes plural elements. For example, the frac plug 200 has a central,interior, mandrel 202 on which all the other elements are placed. Themandrel acts as the backbone of the entire frac plug. The followingelements are typically added over the mandrel 202: a top push ring 203,upper slip ring 204, upper wedge 206, elastic sealing element 208, lowerwedge 210, lower slip ring 212, a bottom push ring 216, and a mule shoe218.

When a setting tool 300 is used to set the frac plug 200, as illustratedin FIG. 3, the setting tool 300 applies a force F on the push ring 203on one side and applies an opposite force on the bottom push ring 216,from the other side. As a consequence of these two opposite forces, theintermediate components of the plug 200 press against each other causingthe sealing element 208 to elastically expand radially and seal againstthe casing 102. Upper and lower wedges 206 and 210 press not only on theseal 208, but also on their corresponding slip rings 204 and 212,separating them into plural parts and at the same time forcing theseparated parts of the slip rings to press radially against the casing.In this way, the slip rings maintain the sealing element into a tensionstate to seal against the casing of the well and prevent the elasticsealing element from returning to its initial position. When the upperand lower wedges 206 and 210 swage the elastic sealing element to sealagainst the casing, the elastic sealing element elastically deforms andpresses against the entire circumference of the casing.

Traditionally, the setting tool 300 has a main body 301 to which isattached a setting sleeve 304, which contacts the upstream end of thefrac plug 200. A mandrel 306 of the setting tool 300 extends from themain body 301 all the way through a bore 201 of the plug 200, until adistal end 306A of the mandrel exits the mule shoe 218. A disk or nut308 is attached to the distal end 306A of the mandrel 306. If a disk isused, then a nut 310 may be attached to the mandrel 306 to maintain inplace the disk 308. An external diameter D of the disk 308 is designedto fit inside the bore 201 of the mule shoe 218, but also to be largerthan an internal diameter d of the shear ring 216 or another element(e.g., a collet) that may be used for engaging the mandrel.

Because the mandrel 306 extends through the entire frac plug 200 and thedisk 308 applies a force on the bottom part (the part closest to the toeof the well) of the frac plug, this type of plug is called a bottom setplug. A disadvantage of such a plug is the fact that a typical bottomset plug does not allow for an operation that is known in the art as a“ball in place” mode, which means that a ball that is used to close thebore 201 of the frac plug 200 is run into the wellbore along with theplug. This mode is in contrast to a traditional mode in which the fracplug 200 is first set up, the setting tool 300 is removed from the well,and then the ball is pumped down the wellbore, from the surface, to sealthe bore 201 of the frac plug 200. Such an operation increases waterusage, costs, and operational inefficiency. Further, the frac plug shownin FIG. 2 has many parts that need to fit together, which increases itscost. Furthermore, when the frac operation is completed, the frac plugneeds to be removed, which is currently achieved by milling it. Thisprocess further adds to the complexity of the well exploration and alsoadds to the oil extraction cost, as the milling operation is expensiveand time consuming.

Thus, there is a need for a simplified plug design that has fewercomponents, can be manufactured to be easily removable, and also canperform the ball in place operation.

BRIEF SUMMARY OF THE INVENTION

According to an embodiment, there is a top set plug for sealing againsta casing of a well. The plug includes a mandrel having a throughout borethat extends from a top end to a bottom end, a connecting mechanismlocated at the top end of the mandrel, wherein the connecting mechanismis configured to connect to a setting tool and the connecting mechanismis attached with a shear member to the mandrel, a sealing elementlocated around the mandrel and configured to be pushed toward aninternal wall of the casing, an upper wedge configured to push thesealing element against the casing, and a slip ring configured to pushthe sealing element over the upper wedge and also to engage the innerwall of the casing with buttons for preventing the plug to slide alongthe casing. The shear member is manufactured to break before any otherpart of the mandrel to release the connecting mechanism, and there is nolower wedge to push against the sealing element.

According to another embodiment, there is a top set plug for sealingagainst a casing of a well. The plug includes a mandrel having athroughout bore that extends from a top end to a bottom end, aconnecting mechanism that is configured to connect to a setting tool,wherein the connecting mechanism is attached through a shear member tothe mandrel, a sealing element partially located around the mandrel andhaving a top end and a bottom end, wherein the top end is configured tobe pushed toward an internal wall of the casing and acts as a seal whilethe bottom end is configured as a ramp, and a slip ring configured toengage the inner wall of the casing with buttons for preventing the plugto slide along the casing. The bottom end of the sealing element entersinto a bore of the slip ring and pushes the slip ring radially outwardtoward the inner wall of the casing. The shear member is manufactured tobreak before any other part of the mandrel to release the connectingmechanism.

According to yet another embodiment, there is a method for plugging acasing in a well. The method includes a step of attaching a setting toolto a frac plug, wherein a ball is placed inside the setting tool; a stepof lowering the setting tool, the ball and the frac plug to a desireddepth into the casing of the well; a step of activating the setting toolto set up the frac plug, wherein a connection between the setting tooland the frac plug is located at a top end of the frac plug; a step ofremoving the setting tool after the connection between the setting tooland the frac plug is broken; and a step of pressuring the ball to seatonto a seat formed into a mandrel of the frac plug.

BRIEF DESCRIPTION OF THE DRAWINGS

Fora more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic diagram of a well in which a setting tool and aplug have been deployed;

FIG. 2 is a schematic diagram of a frac plug;

FIG. 3 illustrates a setting tool that sets up a frac plug at the bottomof the plug;

FIG. 4 illustrates a top set frac plug;

FIG. 5 illustrates the top set frac plug having a ball seated deepinside an internal mandrel for providing structural reinforcement;

FIG. 6 illustrates an activation of the setting tool for setting the topset plug;

FIG. 7 illustrates a ball from another top set plug interacting with acurrent top set plug;

FIG. 8 illustrates a pattern of a slip ring of the top set plug;

FIG. 9 illustrates a cross-section of the slip ring of the top set plug;

FIG. 10 illustrates another top set plug that has a sealing element asthe top most element;

FIG. 11 illustrates the another top set plug after the setting tool hasbeen removed and a ball is seated inside the plug; and

FIG. 12 is flowchart of a method for setting up the top set plug in acasing of a well.

DETAILED DESCRIPTION OF THE INVENTION

The following description of the embodiments refers to the accompanyingdrawings. The same reference numbers in different drawings identify thesame or similar elements. The following detailed description does notlimit the invention. Instead, the scope of the invention is defined bythe appended claims. The following embodiments are discussed, forsimplicity, with regard to a frac plug. However, the embodiments to bediscussed next are not limited to a frac plug, but they may be appliedto other types of plugs or other devices that need to be set up in anarrow conduit.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with an embodiment is included in at least oneembodiment of the subject matter disclosed. Thus, the appearance of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout the specification is not necessarily referring to the sameembodiment. Further, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

According to an embodiment, a novel frac plug is configured to have lessparts and to be set up at the top part and not at the bottom part as thetraditional plugs. In one embodiment, one or more parts, even all theparts, of the frac plug are made of a dissolvable material so that thereis no need for milling the plug after the frac operation of a givenstage is over. In one embodiment, the novel frac plug can be used in aball in place mode, due to the top set up operation. In yet anotherembodiment, the slip part of the frac plug is configured in a zig-zagpattern to maximize a gripping with the casing. The zig-zag pattern alsoprevents the fingers of the slip part to break apart when in the well.The above noted features may be combined in any desired way for a givenfrac plug, depending on its application.

According to an embodiment illustrated in FIG. 4, a top set plug 410 isconfigured to be set up at a top part. The terms “top” and “bottom” aredefined in this application with regard to a placement of the plug in avertical or horizontal well, where the top points toward the head of thewell and the bottom points toward the toe of the well. Thus, a top partof the frac plug is well defined as being the part that contacts thesetting tool, while the bottom part of plug is the part that is facingtoward the toe of the well and opposite from the setting tool.

The top set plug 410 is shown in FIG. 4 as being part of a system 400that also includes a setting tool 470 that is connected to the top setplug 410. The top set plug 410 is placed inside a casing 102 and has amandrel 412 that is configured with a connecting mechanism 414, at itstop end 412A, so that the connecting mechanism 414 is configured tocontact and connect to an inner sleeve 472 of the setting tool 470. Inone embodiment, the connecting mechanism 414 is a thread and the innersleeve 472 has a mating thread 474. However, in another embodiment, theconnecting mechanism is a breakable pin. Other implementations of theconnecting mechanism may be used by those skilled in the art.Irrespective of the implementation of the connecting mechanism, itensures that the plug 410 is fixedly attached to the setting tool whilethe plug is lowered to the desired location inside the casing.

The connecting mechanism 414 is attached to the mandrel 412 through ashear member 416. The shear member 416 is attached to a flared-upportion 417 of the mandrel 412. FIG. 4 shows the flared-up portion 417of the mandrel having a larger internal diameter D1 than a diameter D2of the remaining portion of the mandrel. The flared-up portion 417 isconfigured in this way to press against an upper wedge 422, and to pushthe upper wedge 422 toward the inner wall of the casing 102, asdiscussed later. The shear member 416 may be made from the same materialas the mandrel 412 and the connecting mechanism 414. However, in oneapplication, these elements may be made of different materials and asseparated parts. In this embodiment, these three elements are madeintegrally as part of the mandrel. When the time comes to separate thesetting tool 470 from the plug 410, the inner sleeve 472 is pulled apartfrom the plug 410 until the shear member 416 breaks and releases thesetting tool. Note that the only part that keeps the plug 410 attachedto the setting tool 470 is the connecting mechanism 414. Once the shearmember 416 breaks, the plug is freed from the setting tool. For thisreason, the shear member 416 is made to break when a desired force isapplied to it. While the shear member 416 is shown in FIG. 4 as beingimplemented as a thin part of the mandrel 412, those skilled in the artwould understand that the shear member may be implemented in differentconfigurations, e.g., made of a material that is weaker than thematerial of the mandrel and the connecting member 414. The shear member416 is shaped and/or made of a material so that is breaks before anyother part of the mandrel.

The bottom end 412B of the mandrel 412 is configured to engage with aguide member 418, for example, through threads 420. Other mechanisms maybe used for attaching the guide member 418 to the mandrel 412. The guidemember 418 may have an external diameter D that is slightly (e.g., about10 to 30%) smaller than an interior diameter of the casing 102, so thatthe guide member guides the plug inside the casing while being loweredto its desired location.

Between the guide member 418 and the connecting mechanism 414, thefollowing elements are distributed along the mandrel 412. Starting fromthe connecting mechanism 414, the upper wedge 422 (or tapered cone orramp or wedge-shaped body) is distributed around the mandrel and isconfigured to push radially out on a sealing ring element 424. The ramppart 422A of the upper wedge 422 contacts directly the underside of thesealing ring element 424 and pushes the sealing ring element toward thecasing 102 when the upper wedge 422 is pushed by the external sleeve 480of the setting tool 470. The upper wedge 422 may include one or moreseals 423, that are placed between the upper wedge body and the mandrel412, to prevent a well fluid to move past the upper wedge. The sealingring element 424 also can include one or more seals 425A and 425B,located between the sealing element and the casing and/or the upperwedge 422 to further prevent the escape of the well fluid past the plug410. Note that all these elements of the plug 410 are shown in FIG. 4 asbeing separated from each other by a considerable distance when in fact,this distance is infinitesimal or non-existent, i.e., these elements aretightly packed together. The large distance between these elements isused in this figure to more clearly illustrate each element and therelationships between these elements.

The plug 410 also includes a slip ring 426 disposed around the mandrel412. In one embodiment, the plug includes only one slip ring. The slipring 426 includes one or more buttons 428, which are made from a hardmaterial, and are configured to directly engage with the casing 102 whenthe frac plug is set. The direct contact between the buttons 428 and thecasing 102 ensures that the plug does not move along a longitudinal axisX of the well when the plug is exposed to an upstream pressure.

A bore 413 of the mandrel 412 is configured to have one or two seats. Aseat is defined herein as being a portion of the mandrel, in the bore,that is shaped to receive and mate a ball 440. For example, the mandrel412 may be shaped to have a large seat 430 or a smaller seat 432. In oneembodiment, the mandrel 412 may be shaped to have both seats. The largeseat 430 is a side seat, i.e., it is formed at the side of the mandrel412. However, the smaller seat 432 is an internal seat, i.e., it isformed in a region of the bore that is not at the side of the frac. Anadvantage of having an internal seat is that when the ball 440 is seatedagainst such deep seat 432, as shown in FIG. 5, the ball 440 exerts aforce 510 (only one force is shown although the ball exerts the sameforce all around the mandrel 412) on the mandrel 412, which structurallysupports the entire plug 410 from being compressed along the radialdirection by the pressure exerted by the pumped fluid in the well. Inother words, because the ball 440 is seated deep into the plug 410, asshown in FIG. 5, the deep-set ball imparts additional structuralintegrity to the plug in that it resists an inward radial movement ofthe slips and wedge, which would otherwise loosen the plug's grip on thecasing. It is noted that if one or more elements of the plug moveradially inward toward the central point of the bore 413, a seal betweenthe sealing ring element 424 and the casing 102 may be weakened, whichmay result in the collapse of the plug and the well fluid rushing pastthe plug.

The inventors have found that by having the plug 410 configured to allowthe ball 440 to enter deep inside the mandrel 412, i.e., at least pastthe ends of the mandrel, for example, close to a middle point of themandrel, as shown in FIG. 5, it achieves this structural advantage. Inone embodiment, the ball 440 is considered to enter deep inside themandrel 412 when the ball is at the same position, along thelongitudinal axis X, as the sealing ring element 424, or as the slipring 426. Note that FIG. 5 shows the frac plug 410 being set, i.e., theshear element 416 has been broken, so that the setting tool 470 has beenfreed and removed (although spaces between the elements of the plug andalso spaces between the plug and the casing are still shown).

Returning to FIG. 4, the setting tool 470 is configured to carry theball 440 while also being attached to the plug 410, i.e., to be able toperform the ball in place mode. For this mode, the ball 440 is placedinside the inner sleeve 472 of the setting tool. To prevent the ball 440from moving unintentionally while the setting tool is moved in the wellto the desired position where the plug needs to be set up, the outermandrel 480 includes a retention element 482, for example a pin, thatprevents the ball from moving upstream. To prevent the ball to move in adownstream direction, the inner sleeve 472 includes a retainingmechanism 476, for example, a spring. The ball 440 is placed between theretention element 482 and the retaining mechanism 476 while the settingtool is lowered into the casing. As the setting tool and the ball movedownstream in the casing, the fluid well needs a passage to bypass thistandem. For this reason, one or more slots 484 may be made into theexternal sleeve 480. In this way, the fluid well 490 is able to passthrough the setting tool 470 and through the bore 413 of the plug 410,as indicated by path 492.

The retention element 482, which is fixedly attached to the externalsleeve 480, is allowed to move relative to the inner mandrel 472, topush the ball 440 past the retaining mechanism 476, due to a slot 473formed into the wall of the inner mandrel 472. In this way, when theplug 410 needs to be set, and the setting tool 470 is activated so thatthe internal sleeve 472 moves upstream while the outer sleeve 480remains stationary (or the other way around), the retention element 482effectively moves downstream relative to the inner sleeve 472, andpushes the ball 440 over the retaining mechanism 476. Once the ball 440has moved past the retention mechanism 476, due to the well pressureexerted by the pumps at the well head, the ball 440 moves until isseated in the large seat 430, or the deep seat 432, depending on itssize. Note that if the ball 440 is sized to seat the large seat 430, itcannot move past this seat to reach the deep seat 432.

FIG. 6 illustrates the situation in which the setting tool 470 has beenactivated, the external sleeve 480 is preventing the upper wedge 422from moving along the axial direction X, the inner sleeve 472 has movedin an upward direction relative to the external sleeve 480, opposite tothe longitudinal direction X, thus pulling the mandrel 412 along thesame direction. As a consequence of the movement of the mandrel 412while the upper wedge 422 is stationary, the guiding element 418 hasmoved toward the upper wedge 422, pressing the slip ring 426 and thesealing ring element 424 up the ramp of the wedge element 422, so thatthe sealing ring element 424 is pressing against the casing 102,effectively sealing the casing's bore.

In addition, the retaining mechanism 476 has also moved toward theretention element 482, thus forcing the ball 440 to move past theretaining mechanism 476, as shown in the figure. The ball 440 is nowfreed and when the fluid 490 is pressurized from the surface and movesalong direction 492, it moves the ball 440 into the large seat 430 orthe deep seat 432, depending on the size of the ball. Note that FIG. 6shows the setting tool 470 being activated but not yet freed from themandrel 412.

FIG. 7 shows the ball 440 being seated in the deep seat 432 and thesetting tool 470 freed from the plug 410 as the inner mandrel hasexerted the force on the plug 410 and the shear member 416 broke. Alsonote that the mandrel 412 has been moved together with the guidingelement 418 relative to the other members of the plug 410, so that theupper wedge 422 is now removed from the large seat 430. The upper wedges422 was either in direct contact with the large seat 430 in FIG. 4, orvery close to it.

FIG. 7 shows that one or more slots 434 may be formed in the bottom end412B of the mandrel 412 so that when a ball 440′ from a previous fracplug is contacting the bottom end 412B, the fluid inside the well stillcan pass from the toe of the well toward the head (e.g., during abackflow operation) of the well, past this ball and the frac plug. FIG.7 further shows how the ball 440 seated in the deep seat 432 providesstructural support to the upper wedge 422 and the slip ring 426, toprevent these elements from moving radially inward, toward the bore 413of the mandrel 412. In one embodiment, the deep seat 432 is formed inthe mandrel so that the deep seat is directly opposite to the slip ring426 relative to the mandrel. In another embodiment, the deep seat ismanufactured to be located directly across the upper wedge 422. In stillanother embodiment, the deep seat is manufactured to be located acrossthe sealing element 424. One skilled in the art would understand fromthis disclosure that the deep seat 432 can be formed anywhere internalto the mandrel to be across any of the elements to support them. When alarge pressure is applied to the well fluid, the mandrel 412 can sliderelative to the sealing element 424 and the upper wedge 422, asillustrated in FIG. 5, due to the force imparted by the ball 440. Due tothe flared-up part 417 of the mandrel, it can add additional support tothe upper wedge 422.

In one embodiment, to enhance the adherence of the slip ring 426 to thecasing 102, the slip ring 426 is configured to have a ring 810 andalternating slots 812, which partially extend radially around the ring810 to form a zig-zag pattern, as illustrated in FIG. 8. Note that thebuttons 428 may be configured to have a surface inclination relative tothe casing, such that a better grip between the buttons and the casingis obtained. This zig-zag patterned slip(s) then maximizes the surfacearea gripping the casing wall, thereby increasing the axial hold force.In other embodiments, the slips may be made of several fingers formedfrom slots all extending from one end of the ring. An advantage of thealternating slots 812, or zig-zag patterned slips, is that upon setting,the slip ring 426 will have a tendency to remain intact as compared tothe individual fingers. If a finger or section of the slip ringseparates, it may dislodge from the others, thereby weakening the plug'sadherence to the casing. The buttons 428 of the slip ring 426 “bite”into the casing 102 and increase the axial holding force of the plug. Inthis context, the “axial hold force” refers to the resistance to axialmovement along the longitudinal axis X of the wellbore casing 102.Typically, the force is expressed in terms of the wellbore pressure (inpounds per square inch (psi)) times the sealed inner area of the casingrequired to overcome the plugs adherence to the casing inner wall andmove the plug axially.

A sectional view of the slip ring 426 is shown in FIG. 9, together withtwo cross-sections AA and BB from FIG. 8. FIG. 9 shows the ring 810 andthe fingers 814 that are connected to the ring 810. The slots 812between the fingers 814 are shown being positioned in a firstconfiguration, toward the bottom end 412B, then those at the top end412A. FIG. 9 shows that the slots at the two ends are offset with agiven angular displacement, for example, 90 degrees.

In one embodiment, the plug 410 components may be manufactured asmachined or molded composites, or as dissolvable materials or acombination of the two. In one application, all the parts of the plug410 are made of dissolvable materials. This means that after the fracoperation for a given stage is completed, instead of using a drill tomill the plug, the well fluid or a special fluid is pumped into thewell, which after interacting for a given amount of time with the plug,dissolves the components of the plug. This is very advantageous becauselowering in the well the drilling equipment is time consuming and thus,expensive.

When the traditional plug of FIG. 2 is compared to the novel plug 410 ofFIG. 4, one can observe that the plug 410 has less components. Forexample, the plug 410 does not have the upper slip ring 204 and theupper wedge 206. In one embodiment, the plug 410 also does not have thebottom push ring 216. Because of these features, a volume of the plug410 may be reduced to less than 80 in³, from a volume of 250 in³, whichcustomary for an existing frac plug. Further, the reduced volume of theplug 410 ensures, in one application, that the well fluid that passesthrough it is increased, which prevents large pressure differentialsacross the plug.

In another embodiment, as illustrated in FIG. 10, a frac plug has evenless components than the plug 410 discussed above. A frac plug relies onthe structural integrity of its components to withstand the stressesapplied during its use in the well. The available plugs do not use theball or a restrictive plugging element to aid in the support of the plugduring the frac operation. As such, the available plugs use forcesupportive members (ramps or wedges) that may or may not be backed up byinner mandrels to preserve the overall structural integrity. However,such mandrels have an overall inner diameter just less than about 2.0″.This design often results in plugs longer than 18″ with a total volumeexceeding 250 in³ (in a typical 5.5″ casing application).

This configuration restricts the amount of well fluid that can betransmitted through the plug when advancing through the well. Thus, thisexisting configuration may create large pressure differentials acrossthe plug.

Furthermore, the available plugs use opposing taper angles or ramps ofwedges 206 and 210, as illustrated in FIG. 2, to draw either a sealingarea 208 or a gripping area 212 of the plug into its final set position,against the wall of the casing. The opposing ramps design also requiresexcess plug length as the full travel of the ramps needs to be includedin both the swaging element and the element to be expanded (the seal).

The novel plug 1010 shown in FIG. 10 overcomes these problems by placingthe sealing element 1024 at the top end of the plug. This means thatthere is no wedge or ring or other element upstream of the sealingelement 1024 for pushing onto the sealing element, as is the case forthe existing frac plugs. In addition, this plug is configured, similarto the plug 410, to be a top set plug. The sealing element 1024 isconfigured to have two functions: the top end part 1024A acts as thesealing member while the bottom end part 10246 is shaped and acts as aramp for driving the slip ring 1026 toward the casing 102. In otherwords, the bottom end part 1024B of the sealing element 1024 acts as theupper wedge 422. The slip ring 1026 may have buttons 1028, similar tothe slip ring element 426.

An inner mandrel 1012 allows for load transfer between the setting tool1070, which is attached at the top end 1012A of the mandrel, and theguiding element 1018, which is located at the bottom end 1012B of themandrel. In this embodiment, the guiding element 1018 is attached to themandrel 1012 by a shoulder 1019, which is configured to fit in acorresponding groove 1015 formed in the outer wall of the mandrel 1012.In another embodiment, the guiding element 1018 may be attached withthreads, as the guiding element 418 in FIG. 4. Those skilled in the art,having the benefit of this disclosure, might chose various otherimplementations for this element. The setting tool 1070 is configured,similar to that of FIG. 4, to connect to the upper part of the mandrel1012, for example, through a connecting mechanism 1014 that connects tothe inner sleeve 1072. In this figure, the connecting mechanism 1014 isimplemented as threads. However, the connecting mechanism may beimplemented as a breakable pin, etc. A shear member 1016 is present onthe mandrel 1012 to allow the top part to break away after the settingtool has set up the plug. FIG. 10 further shows the outer sleeve 1080 ofthe setting tool being in direct contact with the sealing member 1024.

The frac plug 1010 further includes a single piece slip 1026, whichincludes a base ring 1027 with slips 1029 machined such that they areattached solely at the base of each geometric slip section. Included onthe outward surface of the slip 1026 is a hardened insert or button1028. This hardened material may be comprised of ceramic, carbide, castiron, etc. A transitionary seal 1023 may be located between the mandrel1012 and the sealing element 1024. The transitionary seal allows theplug to actuate through its full range of motion while maintaining thepressure differential integrity. This feature is not required in thatwhen the tool is in its fully set state and has been stroked down due towellbore isolation pressures, a metal to metal seal may be achievedbetween the mandrel 1012 and the main swage body.

One or more grooves 1025 may be formed in the sealing element 1024,facing the casing 102, and they are aiding in obtaining a positive metalto metal seal between the frac plug outer diameter and the innerdiameter of the cased wellbore. These grooves can be either ran as shownor with the addition of an elastomeric sealing element nested insideeach groove.

The frac plug 1010 and the setting tool 1070, configured as discussed inthis embodiment, can carry a ball 1040 while being deployed from thesurface, thus being capable of achieving a ball in place mode. After thesetting tool 1070 is activated and removed from the plug, the ball 1040enters inside the plug 1010, and seats on the deep seat 1032, as shownin FIG. 11, thus sealing or blocking a bore 1013 of the mandrel 1012.The deep seat 1032 is located under the sealing element 1024, so thatthe force F that is applied by the well fluid 1090 onto the ball 1040 ispartially spread radially outward on the inner wall of the sealingelement 1024, to enhance the integrity of the seal and to further pressthe sealing element against the inner wall of the casing 102. In oneembodiment, the deep seat is configured to be across the slip ring 1026.While FIG. 11 shows that the ball 1040 interacting only with the deepseat 1032, formed in the mandrel 1012, in one embodiment it is possibleto configure the plug 1010 so that the ball 1040 also directly contactsthe sealing element 1024.

A method for plugging a casing in a well for a frac operation is nowdiscussed with regard to FIG. 12. The method includes a step 1200 ofattaching a setting tool to a frac plug, wherein a ball is placed insidethe setting tool, a step 1202 of lowering the setting tool, the ball andthe frac plug to a desired depth into the casing of the well, a step1204 of activating the setting tool to set up the frac plug, wherein aconnection between the setting tool and the frac plug is located at atop side of the frac plug, a step 1206 of removing the setting toolafter the top connection between the setting tool and the frac plug isbroken, and a step 1208 of pressuring the ball to seat into a deep seatinside a mandrel of the frac plug, away from a top end and a bottom endof the mandrel, to provide structural support to the frac plug. In oneapplication, the frac plug has a single wedge, for example, the upperwedge and not a lower wedge. In another application, the frac plug 410has only the elements shown in FIG. 4 and the frac plug 1010 has onlythe elements shown in FIG. 10, i.e., much less elements than theexisting plug 200.

The disclosed embodiments provide a top set plug for use in a well forisolating one stage from another. The top set plug is configured to haveless parts than an available plug. It should be understood that thisdescription is not intended to limit the invention. On the contrary, theembodiments are intended to cover alternatives, modifications andequivalents, which are included in the spirit and scope of the inventionas defined by the appended claims. Further, in the detailed descriptionof the embodiments, numerous specific details are set forth in order toprovide a comprehensive understanding of the claimed invention. However,one skilled in the art would understand that various embodiments may bepracticed without such specific details.

Although the features and elements of the present embodiments aredescribed in the embodiments in particular combinations, each feature orelement can be used alone without the other features and elements of theembodiments or in various combinations with or without other featuresand elements disclosed herein.

This written description uses examples of the subject matter disclosedto enable any person skilled in the art to practice the same, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the subject matter is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims.

1. A top set plug for sealing against a casing of a well, the plugcomprising: a mandrel having a throughout bore that extends from a topend to a bottom end; a connecting mechanism located at the top end ofthe mandrel, wherein the connecting mechanism is configured to connectto a setting tool and the connecting mechanism is attached with a shearmember to the mandrel; a sealing element located around the mandrel andconfigured to be pushed toward an internal wall of the casing; an upperwedge configured to push the sealing element against the casing; and aslip ring configured to push the sealing element over the upper wedgeand also to engage the inner wall of the casing with buttons forpreventing the plug to slide along the casing, wherein the shear memberis manufactured to break before any other part of the mandrel to releasethe connecting mechanism, and wherein there is no lower wedge to pushagainst the sealing element.
 2. The plug of claim 1, wherein the mandrelhas a deep seat formed away from the top and bottom ends of the mandrel.3. The plug of claim 2, wherein the deep seat is formed directly acrossfrom the slip ring, or directly across from the upper wedge, or directlyacross from the sealing element.
 4. The plug of claim 1, wherein theslip ring is the only slip ring of the plug.
 5. The plug of claim 1,further comprising: a second seat formed at an end of the mandrel, awayfrom the deep seat.
 6. The plug of claim 1, wherein the mandrel has aseat formed at the top end.
 7. The plug of claim 1, wherein the entireplug is formed of one or more dissolvable materials.
 8. The plug ofclaim 1, wherein at least one of the mandrel, the sealing element, theupper wedge, and the slip ring are formed from a dissolvable material.9. The plug of claim 1, further comprising: a guiding element fixedlyattached to the bottom end of the mandrel.
 10. The plug of claim 1,wherein the mandrel has a flared-up part that is configured to push theupper wedge toward the sealing element and also radially away from alongitudinal axis of the mandrel.
 11. A top set plug for sealing againsta casing of a well, the plug comprising: a mandrel having a throughoutbore that extends from a top end to a bottom end; a connecting mechanismthat is configured to connect to a setting tool, wherein the connectingmechanism is attached through a shear member to the mandrel; a sealingelement partially located around the mandrel and having a top end and abottom end, wherein the top end is configured to be pushed toward aninternal wall of the casing and acts as a seal while the bottom end isconfigured as a ramp; and a slip ring configured to engage the innerwall of the casing with buttons for preventing the plug to slide alongthe casing, wherein the bottom end of the sealing element enters into abore of the slip ring and pushes the slip ring radially outward towardthe inner wall of the casing, and wherein the shear member ismanufactured to break before any other part of the mandrel to releasethe connecting mechanism.
 12. The plug of claim 11, wherein the mandrelhas a deep seat formed away from the top and bottom ends of the mandrel.13. The plug of claim 12, wherein the deep seat is formed directlyacross from the slip ring.
 14. The plug of claim 12, wherein the deepseat is formed directly across from the sealing element.
 15. The plug ofclaim 11, wherein the entire plug is formed of one or more dissolvablematerials.
 16. The plug of claim 11, wherein the sealing element is thefirst element of the plug at the upstream end of the plug.
 17. The plugof claim 11, further comprising: a guiding element fixedly attached tothe bottom end of the mandrel.
 18. A method for plugging a casing in awell, the method comprising: attaching a setting tool to a frac plug,wherein a ball is placed inside the setting tool; lowering the settingtool, the ball and the frac plug to a desired depth into the casing ofthe well; activating the setting tool to set up the frac plug, wherein aconnection between the setting tool and the frac plug is located at atop end of the frac plug; removing the setting tool after the connectionbetween the setting tool and the frac plug is broken; and pressuring theball to seat onto a seat formed into a mandrel of the frac plug.
 19. Themethod of claim 18, wherein the seat is a deep seat, which is locatedaway from the top end and a bottom end of the mandrel, to providestructural support to the frac plug.
 20. The method of claim 18, whereinthe frac plug has only an upper wedge and not a lower wedge.
 21. Themethod of claim 18, wherein one or more elements of the frac plug aremade of a dissolvable material.